Yeah I can see it being like Black/White Kyurem. A "boss" battle and then you can actually catch them later on after beating them with the special ball(s).i dont see why UBs cant be maingame bosses that are basically glorified Totems with all the perks - autobuff, uncatchable, calls in reinforcements - and be relegated to postgame only for catching them with that Aether Ball(name mine, it's not in the datamine).
it doesnt really stop them from being 'threats' as advertised. the fact that they need a unique pokeball also points to them being not-pokemon that, well, function as pokemon anyway. so they're the same, but different... but still same.
sidenote: does anyone else find it crazy that humans in the pokemon world took a short look at these UBs, presumably tried to catch them with pokeballs, and decided they really wanted them to the point that they made compatible capturing devices? that's pretty hardcore.
At the very least if Beauty isn't a SOS battle i'm not sure what else could be.